A whole series of pigments are known based on zirconium silicates in which the lattice configuration of the zirconium silicate has built into it color forming metal ions; such as for example, zirconium praseodymium yellow or zircon vanadium blue.
In U.S. Pat. No. 2,441,447, there is described blue and green pigments based on zirconium silicate-vanadium oxide which are produced through calcination of zirconium-, silicon- and vanadium compounds at temperatures above 550.degree. C. In the case of the blue pigments, the yield contains in addition to up to 17% by weight vanadium oxide additionally up to 5 weight percent of alkali halogenides. Green pigments result only in the absence of alkali halogenides and arise from a mix of vanadium doped yellow zirconium oxides, vanadium doped blue zirconium silicate and silicon oxide. The prior art deals therefore with a mixed pigment and not with a unitary pigment type as would be desired because of industrial application purposes.
In the publications of Th. Goldschmidt, 2/83, No. 59, there is described on page 13 a zircon-vanadium blue pigment. Herewith are used a variety of sodium salts such as sodium fluoride, sodium chloride, Na.sub.2 CO.sub.3, Na.sub.2 SO.sub.4 and NaNO.sub.3 as flux material for the preparation of the known zirconium-vanadium blues. As contrasted therewith, the corresponding lithium and potassium salt lead mostly to a greenish-blue colored pigment. This document provides no information for the preparation of a gray-green zirconium-vanadium pigment body.